function mx_close_eyelink_connection( )
%MX_CLOSE_EYELINK_CONNECTION  Closes any connection to the eye tracker, and 
% closes the link.
%
% Remarks:
% NEW (v2.1): Broadcast connections can be closed, but not to affect the eye 
% tracker. If a non-broadcast (primary) connection is closed, all broadcast 
% connections to the tracker are also closed.
%
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% Copyright Eduardo Aponte 2013
% aponteeduardo@gmail.com